#include<stdio.h>
int a[102], b[102];
int v[102];
int main()
{
	int n, m;
	scanf("%d %d", &n, &m);
	int i;
	for (i = 0; i < m; i++)
		scanf("%d %d", &a[i], &b[i]);
	for (i = 0; i < n; i++)
		v[i] = 0;
	for (i = 0; i < m; i++)
		v[b[i] - 1]++;
	int ans = 0;
	for (i = 0; i < n; i++)
		if (v[i] == 0)
			ans++;
	printf("%d\n", ans);
	return 0;
}